Composition and method for treating polluted waters and water sediments

ABSTRACT

A composition having a depot effect and a method for treating polluted waters and water sediments such that constituents that are hazardous to water are essentially decomposed or bound. Microbiological decomposition processes are long-term supported and water quality is improved without adding salt or decreasing the pH value. The composition contains one or more compounds which are produced by converting iron(III) nitrade and/or aluminium nitrade and hydrogen peroxide in the presence of a base and release oxygen and/or nitrations as oxygen donors in a prolonged manner when contacting water.

BACKGROUND OF THE INVENTION

The invention relates to a composition and method for treating pollutedwaters and water sediments as described herein.

Treatment of waters and revitalizing natural bodies of water isincreasingly important. The influx of nutrients from domestic andindustrial waste water, detergents and rinse agents, sewage, chemicalfertilizer, etc., which increases from year to year, as well as theincreasing acidity of the water due to acidic inflow disturbs thenatural balance of the waters and impedes the natural self-cleaningability of the waters.

As a result, pollutants and nutrients build up in the waters and in thewater sediments. These processes can cause dramatic shifts in thepopulation of species in the entire ecosystem. This causes largevariations in the oxygen content in the water body and an oxygendeficiency in the water layer close to the sediment and/or in thesediments themselves, accompanied by a remobilization of nutrients andpollutants.

Conventional techniques use flocculation with Fe(III)-salts and aluminumsalts for removing water ingredients. Water ingredients which areunaffected by precipitation processes can be removed by inclusion in orabsorption on the flake. DE-AS 19 07 359 discloses the use of aluminumsulfate and chloride, Fe(II)- and Fe(III)-sulfate, Fe(II)- andFe(III)-chloride and the like. The generated flakes, however, can have asedimentation characteristic that is inadequate for natural bodies ofwater; in particular, iron salts have a tendency for forming colloidalprecipitates.

Disadvantageously, the flocculation means can leave anions in the waterwhich can increase the salinity and acidity of the water. Also used arebase metal salts of the chemical formula Mn (OH)_(m)X_(3n−m), wherein Mrepresents Fe(III) and aluminum, and X is a monovalent anion; inaddition, a polyvalent anion Y of a divalent or polyvalent acid (forexample, phosphoric acid, silicic acid, chrome acid, carbonic acid,sulfuric acid) with a very small mole ratio was introduced in thecompound (DE-AS 19 07 359).

The application of flocculation means of this type for the purpose ofrestoring lakes has not been successful, because the size of thegenerated flakes caused lasting damage to the plankton population.

To eliminate the disadvantages associated with the increased salinityand acidity of the water, it was proposed to add Fe(III)- and/oraluminum nitrate to the water and to subsequently reduce the nitrateions to molecular nitrogen. This reduction can take place, for example,by denitrification (DE 38 38 864).

The method was developed, in particular, to satisfy the requirements forwaste water treatment. The employed nitrates dissolve well in water;however, no sedimentation of the nitrate ions should be expected. Sincethe matter to be treated with nitrate are predominantly restingorganisms, the substrate and the biomass have to be kept in constantcontact with each other.

U.S. Pat. No. 5,500,131 discloses treating water with calcium carbonate(lime) and metal salts as flocculation means. The metal salt used arealuminum- and iron-chlorides, -sulfates and nitrates.

The use of the products for an effective treatment, however, is limitedto the water body itself. The sedimented flakes form a gas-permeablemembrane on the sediment surface and simultaneously acts as a coverlayer. The break-down of organic sediments itself is only slightlyenhanced.

Also known is the treatment of the sediments on the bottom of bodies ofwater with lime and fermentation fungi with additional aeration of thesludge (JP 60-106 592 A). Although this enhances the break-downprocesses, the introduction of foreign organisms almost always carrieswith it a substantial risk for the ecosystem and requires lengthyapproval processes.

DE-40 05 064 C describes treating water sediments with FeO, Fe(OH)₂and/or Fe(OH)₃ under addition of oxygen and motion. This approachenhances the biological break-down and binds phosphates and hydrogensulfite. The hydrogen sulfite can be reduced in the presence of asufficient amount of oxygen to elemental sulfur, which then precipitateson the bottom of the waters.

This treatment typically requires agitating the water to introduceoxygen which can swirl and displace the sludge on the bottom of thewaters. The process is limited by the oxygen saturation limit of thewater and/or by the large amount of mechanical energy required toagitate the water.

DE 34 30 484 A1 describes a method for an oxidizing treatment of wastewater with specially activated carbon carriers that include Fe(III)(NO₃)₃ and with H₂O₂ as oxidant. The carbon carrier is activated byanodic oxidation in mineral acids. The formation of nitrate-containingamorphous iron-oxihydrate structures should be prevented. Nomacro-porous flake structure is formed.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a simple and effectivemethod and a composition for the treatment of waters and watersediments, which can reduce or bind ingredients that pollute the waterto the greatest possible extent, can promote long-term microbiologicalreduction processes, and can improve the water quality, withoutincreasing the salinity or decreasing the pH value of the water. Inparticular, phosphates and heavy metal ions should be rendered harmlessand/or their ecological toxicity reduced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The object is solved by the invention described herein. The compositionof the invention is characterized in that it contains one or morecompounds which are produced by reacting Fe(III) nitrate and/or aluminumnitrate and hydrogen peroxide in the presence of a base, and whichrelease over a long period of time oxygen and/or nitrate ions as oxygendonors upon oontact with water.

The compositions according to the invention have not only a highabsorbency for nutrients and pollutants, but also a depot effect foroxygen and oxygen donors.

The composition according to the invention contains modified Fe(III)-and/or aluminum-containing compounds with depot properties.

It has been observed that Fe(III)- and/or aluminum-containing compoundsare formed by reacting Fe(III) and/or aluminum nitrate with hydrogenperoxide in the presence of a base. The formed compounds have a largespecific surface area and include in their structure oxygen in form of adepot. The nitrate ions act as oxygen donors.

Surprisingly, the fabrication method of the invention promotes inclusionof nitrate ions and oxygen in the structure of the composition in such away that they are slowly released in the waters and particularly on andin the water sediment.

The successive release of oxygen and nitrate ions provides these oxygenand nutrient sources to the microorganisms over a longer time, whichpromotes the biological break-down processes in the waters and the watersediment and increases their effectiveness.

The nitrate ions are hereby completely reduced to oxygen and nitrogen,which eliminates the accumulation of nitrates in the waters and watersediment. The oxygen released by the biological processes is availableto the microorganisms, while the nitrogen escapes.

The released oxygen and the nitrate ions can also aid through oxidationin the removal of organic pollutants that are present in the waters orthe water sediments. Anaerobic processes that cause the formation of H₂Sare suppressed.

The successive release of oxygen and nitrate ions have another importantadvantage of promoting oxidizing reactions which can regenerate suitablebinding partners for pollutants and nutrients, thereby increasing thebinding and retention capacity of the Fe(III)- and/oraluminum-containing compounds.

The successive release of oxygen and nitrate ions prevents the reductionof Fe(III)-ions to Fe(II)-ions which is ineffective for the binding andattachment processes. These processes also increase the binding capacityof the composition of the invention for pollutants and nutrients, inparticular, for phosphates and heavy metals.

In addition, with the composition of the invention, sulfide ions arebound in a water-insoluble form. The sulfur is herein precipitated asiron sulfide and immobilized in the sediment. This can significantlyreduce the toxicity and odor emission from H₂S. These conventionalprocesses are affected by the composition of the invention in that theoxygen, which is successively released from the composition, causes afurther reduction of the iron sulfides to elemental sulfur which depositin the sediment. Since the iron released from the sulfide is availableas a binding partner for additional binding and precipitation processes,the capacity and the effectiveness of the binding and/or attachment ofpollutants and nutrients is significantly enhanced.

The compositions of the invention also bind the phosphate ions which arepresent in the water and/or sediment in form of Fe(III)- and/or aluminumphosphate. The bound phosphates deposit in the water sediment and arethen no longer accessible to the producers (algae) to support theirmetabolism. The heavy metals are also irreversibly incorporated in thestructure of the modified Fe(III)- and/or aluminum-containing compoundsof the invention or absorbed thereon, which reduces their ecologicaltoxicity.

The macro-porous flake structure of the composition of the invention isparticularly advantageous for these processes due to its significantlygreater absorptive surface area and improved sedimentation properties incomparison to the Fe(III)- and aluminum-salts, which are known in theart as flocculation means.

This significantly increases the capacity and effectiveness for bindingpollutants and nutrients.

The condensation progresses while the hydrogen ion concentrationdecreases due to the dilution of the solution with water or the additionof the base, until three-dimensional high-molecular colloidalcondensates (network structure) of the overall composition(FeOOH)_(x)×H₂O form, which are less and less soluble and finallyprecipitate as agglomerates in the form of large flakes.

Due to the particular structure of the compositions of the invention,ingredients in the water can be removed which cannot be bound with theconventional precipitation means, such as bulky forms of algae.

Moreover, the composition of the invention—due to its structure—forms anexcellent substrate for the settlement of microorganisms and thereforealso supports the biological cleaning effect.

By binding and attaching the nutrients, in particular phosphates, thealgae are deprived of an essential basis for growth, which prevents thedevelopment of algae masses. Moreover, reductive hostile environmentalfactors are eliminated in the long run due to the successive releases ofoxygen.

It was also found that the compositions according to the invention forma skeletal-like structure for the treatment of water and watersediments.

The depot effect, however, is not limited to oxygen and nitrate ions.Additional compounds, for example sulfates such as iron sulfate, can beadded as oxygen donors in the manufacturing process. Other sulfate ions,such as CaSO₄ or MgSO₄, can be added, which represent compound thatoccur naturally in the waters. However, no more than 50 wt. % sulfateions should be added, based on the nitrate ions present in the waters.

Moreover, additives which may be useful for water restoration of aspecific body of water can be added in the manufacturing process or formin the manufacturing process from the corresponding starting materials.One example is the addition of CaCO₃ to the water or the sediment.

These polar compounds are likewise included into the skeletal structureof the Fe(III)- and/or aluminum-containing compound and alsosuccessively released in the water and/or the water sediment.

This makes feasible the application of the compounds of the inventionfor a comprehensive and lasting restoration of bodies of water withoutthe need for additional treatment steps. The composition of theinvention is produced by reacting Fe(III)- and/or aluminum nitrate withhydrogen peroxide in the presence of a base.

The reaction advantageously takes place at a pH value above 6,preferably at a pH value between 7 and 10, whereby the pH value isadjusted by using a base.

The hydroxides of monovalent, divalent and/or trivalent metals, inparticular calcium, magnesium, sodium and potassium, are used as a base.

Preferably, calcium hydroxide and magnesium hydroxide are used, sincethese bind any carbonates, sulfates and phosphates already present inthe water by forming difficult to dissolve precipitates.

The reaction can advantageously take place in the presence ofconventional oxidation catalysts.

Optionally, the composition of the invention can be produced in thepresence of supplementary additives required for the restoration ofwaters. Depending on the water quality and the task at hand, CaCO₃ canbe added during manufacture, for example, to enhance the bufferingcapacity of the system.

For example, additional phosphates, amino acids, fatty acids, and humineacids can be extracted from the water body by initiating thewater-internal calcite precipitation, thus significantly enhancing thecapacity of the sediments to bind nutrients.

The compositions produced according to the invention have the ability tosediment relatively quickly after being introduced in the water and toabsorb nutrients on their sedimentation path. They initially form abarrier layer on the sediment surface against the phosphate that isremobilized from the sediment. In a subsequent step, the remobilizedphosphate attaches to the amorphous iron, aluminum or calcium surfaces.During the gradual invasion into the water sediment, oxygen and nitrateions slowly desorb and thereby provide to the microorganisms the sourcesof oxygen required for aerobic breakdown processes.

Reductice processes that cause the formation of H₂S and mobilize heavymetals are thereby eliminated.

Any residual quantities of hydrogen peroxide do not interfere with thedesired processes, but rather support the breakdown of the hazardoussubstances in the water and the water sediment through oxidation.

The compositions of the invention are used for treating waters and watersediments loaded with nutrients and pollutants.

They are produced by a simple manufacturing process according to theinvention and added to the water in a single step without the need foradditional processing, purification, separation and the like. Due to thesimple technology and low energy cost both for producing the compositionand for the water treatment, the entire process for treatment of watersand water sediment loaded with nutrients and pollutants becomes quitesimple and very effective.

By treating the water and water sediment with the compositions of theinvention, phosphates are immobilized, sulfates are bound, heavy metalsare converted into compounds that are less toxic for the environment,and microbiological breakdown processes are promoted. This does notincrease the salinity or acidity of the water.

What is claimed is:
 1. Composition with a depot effect, wherein thecomposition comprises one or more compounds, which are produced byreacting Fe(III) nitrate and/or aluminum nitrate and hydrogen peroxidein the presence of a base and the composition releases oxygen and/ornitrate ions as oxygen donors upon contact with water over a long periodof time.
 2. Composition of claim 1, wherein during the reaction betweenFe(III) nitrate and/or aluminum nitrate and hydrogen peroxide, sulfateions are also added at most 50 wt. % based on the nitrate used. 3.Composition of claim 1, wherein the hydroxides of monovalent, divalentand/or trivalent metals are used as the base.
 4. Composition accordingto claim 1, wherein calcium hydroxide and/or magnesium hydroxide areused as the base.
 5. Composition according to claim 1, wherein thereaction takes place at a pH value above
 6. 6. Composition according toclaim 1, wherein the reaction takes place in the presence of oxidationcatalysts.
 7. Composition of claim 1, wherein the reaction takes placein the presence of additives.
 8. Composition according to claim 1,wherein the reaction takes place in the presence of carbonates and/orsulfates.
 9. Method for treatment of polluted waters and watersediments, comprising reacting Fe(III) nitrate and/or aluminum nitrateand hydrogen peroxide in the presence of a base to obtain a suspensioncontaining Fe(III)- and/or aluminum-containing compounds, andintroducing the suspension into the water and/or the water sediments.10. Method of claim 9, wherein during the reaction between Fe(III)nitrate and/or aluminum nitrate and hydrogen peroxide, sulfate ions arealso added at most 50 wt % based on the nitrate used.
 11. Method ofclaim 9, wherein the hydroxides of monovalent, divalent and/or trivalentmetals are used as the base.
 12. Method according to claim 9, whereinthe reaction takes place at a pH value above
 6. 13. Method according toclaim 9, wherein the reaction takes place in the presence of oxidationcatalysts.
 14. Method of claim 9, wherein the reaction takes place inthe presence of additives.
 15. Method according to claim 9, wherein thereaction takes place in the presence of carbonates and/or sulfates. 16.Composition of claim 3, wherein the hydroxides of calcium, magnesium,sodium, and potassium are used as the base.
 17. Composition according toclaim 5, wherein the pH value is between 7 and
 10. 18. Composition ofclaim 7, wherein the additives are materials that are known to restorewaters.
 19. Method of claim 11, wherein the hydroxides of calcium,magnesium, sodium, and potassium are used as the base.
 20. Method ofclaim 12, wherein the pH value is between 7 and
 10. 21. Method of claim14, wherein the additives are materials that are known to restore water.